Such a device is known from DE-AS No. 24 25 800. The device serves to hold an electrode of a spark erosion machine. In that case the other member or coupling member connected firmly to the spark erosion machine has a conical aperture into which is inserted a conical shaft of the member or a part to be retained. The conicities of shaft and coupling member must match as closely as possible. The coupling member further has a transverse opening through which passes a cross bar formed in turn with a central square opening. The conical shaft includes an axial projection with an enlargement which can be pushed through the square opening in the cross bar and locks the shaft at the cross bar after the shaft has been rotated through 90.degree..
The coupling member further has an external thread for cooperation with an internal thread formed in a cap screw. By a shoulder the cap screw presses elastic discs against the cross bar, thus pulling the cone of the shaft into the conical aperture. At the same time, the contact pressure acting on the cone is uncoupled somewhat from the tightening torque of the cap screw because of the elasticity of the discs. In addition a ring is fastened at the opening of the cap screw and comes to rest on an abutment shoulder of the coupling member so that the cap screw can be screwed only up to this stop. Upon loosening of the cap screw the latter ring acts against the cross bar, thereby pushing the conical shaft out of the conical aperture.
This known device is not suited to take up parts which have a different cross sectional shape. In particular the known device cannot establish connection with a cylindrical shaft.
In the case of another known fastening system cylindrical shafts may be used as tool holders or workpiece holders. With this system a die sinking electrode for spark erosion, at first having to be machined itself as a workpiece and then, upon being given its shape, becoming the tool, is fastened by soldering to the end face of a cylindrical shaft. The cylindrical shaft subsequently is placed in a chuck and, when its position with respect to the end face of the chuck has been fixed, both in height and in circumferential direction, the shaft is clamped in position by two pins one of which, protruding from the cylindrical shaft strikes against the end face of the chuck and at the same time against another pin which protrudes axially from the end face. Together with the shaft connected by soldering and acting as a handling aid, the future sinking electrode passes through all the machining steps and, when it has been completed, it is used by the same shaft as the sinking electrode in a die sinking erosion machine.
This solution has the disadvantage of involving expensive soldering of the workpiece or tool on the cylindrical shaft. Besides, not all materials are suitable for soldering. The round shaft entering the chuck furthermore restricts the possibilities of combination upon coupling to the erosion machine. In the case of bigger shaft diameters the parts including the shaft and the tool or workpiece become bulky, heavy, and expensive, and it also becomes difficult to store them for future machining.